Gloucester Security of Supply

In July 2007 output from the Mythe Water Treatment Works was lost, affecting approximately 140,000 customers. In line with recent industry regulations, any treatment works serving a population greater than 20,000 must not be limited to a single source supply. The Gloucester Security of Supply pipeline is the new pipeline which helped provide an alternative supply to the Mitcheldean Works including a 35 Ml/day pumping station.

Consultants Grontmij were tasked with designing the pipeline by Severn Trent Water. Due to mild to severe ground conditions the decision was taken to procure a 600mm coated and lined steel pipeline from FT Pipeline Systems. Two significant advantages lay in the three layer polyethylene coating system which provided superior corrosion protection to the pipe and the ability for a cost effective cathodic protection system to be applied.

Additionally, the pressure rating of the system required suitability for PN25 rating. This was achieved by increasing the steel grade but retaining the lower wall thickness, thereby keeping the price per meter to a minimum for the raw materials.

The scheme comprised over 1250 pipes, 150 bends, tees and other fittings, 1500 Canusa heat shrink sleeves and pipe spacers for auger bore crossings. There was also a horizontal directional drill section of 310m under the River Avon which utilised a mortar coated pipe system – the Mannesmann T-Rib system – a specialist system specifically designed for HDD crossings.